The technological scene is developing towards employing tiny-sized devices. For a variety of functions that encompass sensing, identification, and decision-making. These devices are re-stricted in their resources to be secure. The National Institute of Standards and Technology (NIST) has published the Ascon, a standard lightweight cryptography (LWC) algorithm for data gath-ered by restricted devices in 2023. The fundamental function of Ascon is the permutation function. The main core of the permutation function is the substitution box (S-box). This paper proposes an S-box based on chaotic systems using coupled map lattices (CML), which agrees with LWC al-gorithms due to its low complexity. The proposed S-box suggests high performance and security for restricted devices. The security robustness is tested using various cryptographic criteria, such as nonlinearity, strict avalanche criteria, and differential approximation probabilities. The pro-posed S-box approaches significant resistance to both linear and differential cryptanalysis. So, it could be replacing the substitution and linear diffusion layers of Ascon permutation to improve the nonlinearity and randomness.